1. Field of the Invention
The present invention relates to a powdery molybdenum oxysulfide dithiocarbamate composition, a process for producing same and a grease composition containing the composition. More specifically, the present invention relates to a powdery molybdenum oxysulfide dithiocarbamate composition which exhibits low corrosive action and has excellent lubricating properties, a process for producing it and a grease composition containing the composition.
2. Description of the Related Art
Heretofore, adding molybdenum oxysulfide dithiocarbamate to grease has been tried in order to improve extreme pressure properties, friction modifier properties and anti-wear properties of grease. Various methods for producing such molybdenum oxysulfide dithiocarbamate have been disclosed. For example, Japanese Patent Publication No.45-24562 discloses a method by which a compound having the general formula: EQU [R.sub.2 N-CS-S].sub.2 Mo.sub.2 O.sub.m S.sub.n
(wherein m+n=4, m=2.35-3, n=1.65-1, and R is a hydrocarbyl group having 1 to 24 carbon atoms) can be produced by reacting together a secondary amine, carbon disulfide and molybdenum trioxide.
Japanese Patent Laid-Open No. 48-56202 discloses a method in which a compound represented by the following general formula: ##STR2## (wherein R is an alkyl group) can be produced by reacting the product given by the method of Japanese Patent Publication No. 45-24562 described above with phosphorus pentasulfide.
In addition, Japanese Patent Laid-Open Nos. 52-19629 and 52-106824 disclose methods by which a compound represented by the following general formula: ##STR3## (wherein R.sub.5 and R.sub.6 are independently hydrocarbyl groups having 1 to 24 carbon atoms. l is a number from 0.5 to 2.3, o is a number from 3.5 to 1.7 and l+o=4) can be produced by reacting carbon disulfide with a secondary amine in an aqueous solution or suspension containing molybdenum trioxide or an alkali metal salt or an ammonium salt of molybdic acid and an alkali hydrogensulfide or an alkali sulfide in a molar ratio of 1:0.05-4.
However, the compound of Japanese Patent Publication No. 45-24562 above is inferior in heat resistance and, in the grease preparation process, may cause a color change in the resulting grease. On the other hand, the compound described in Japanese Patent Laid-Open No. 48-56202 exhibits corrosive action against copper plates, thus the use of the compound has been limited. The compound described in Japanese Patent Laid-Open Nos.52-19629 and 52-106824 also still has room for improvement in terms of lubricating properties and corrosive properties. That is, when the powdery molybdenum oxysulfide dithiocarbamate is added to the grease to prepare a grease composition, its physical properties such as particle size have been neglected. As a result, the grease composition produced is not imparted with sufficient lubricating properties, and furthermore may cause slight vibrations.